Method for the manufacture of elastic twisted yarns and textile products



April 7, 1970 A. M. c. ALEXANDRE 3,504,410

METHOD FOR THE MUJIAC'IUREv OF ELASTIC TWISTED YARNS AND TEXTILE PRODUCTS 4 Sheets-Sheet 1 Filed May 3l, 1967 April 7, 1970 A. M. c. ALEXANDRE 3,504,410 METHOD FOR THE MANUFACTURE OF ELASTIC TWISTED YARNS AND TEXTILE PRODUCTS Filed may s1, 19e? 4 Sheets-Sheet 2 April 7, 1970 A. M. c. ALEXANDRE 3,504,410

METHOD FOR THE MANUFACTURE OF ELASTIC TWISTED YARNS AND TEXTILE PRODUCTS Filed May 5l, 1967 4 Sheets-Sheet 3 April 7, 1970 A. M. c. ALEXANDRE 3,504,410

METHOD FOR THE MANUFACTURE OF ELASTIC TWISTED' YRNS AND TEXTILE PRODUCTS Filed May 31, 1967 4 Sheets-Sheet 4 United States Patent O METHOD FOR THE MANUFACTURE OF ELASTIC TWISTED YARNS AND TEXTILE PRODUCTS Albert Marcel Cyprien Alexandre, Saint-Pierre-de- Colombier, Ardeche, France Continuation-impart of applications Ser. No. 357,443, Apr. 6, 1964, and Ser. No. 423,018, Jan. 4, 1965. This application May 31, 1967, Ser. No. 642,505 Claims priority, application France, Apr. 10, 1963, 931,017; Jan. 8, 1964, 959,728 Int. Cl. D02g 3/32 U.S. Cl. 28-72 11 Claims ABSTRACT OF THE DISCLOSURE A process for the manufacture of an elastic twisted yarn whereby an elastic material is twisted and covered by at least one covering yarn, after which the elastic material and yarn are shrunk by thermal treatment in a non-oxidizing atmosphere. An elastic twisted yarn having a twisted core of shrinkable elastic synthetic material covered by at least one covering yarn.

Cross-references to related applications This application is a continuation in part of applicants U.S. patent application Ser. No. 357,443 filed Apr. 6, 1964, and now abandoned and application Ser. No. 423,018 filed Jan. 4, 1965 and now abandoned.

Background of the invention The present invention relates to the manufacture of elastic yarns and of textile products from such elastic yarns.

The manufacture of yarns which are naturally elastic,k in contrast to yarns which are formed from inextensible fibres which may have an artificial elasticity due to the form of these fibres, rather than to the inherent nature of the material of which the said fibres are constituted, is particularly difficult, precisely by reason of the extensibility of the material used. Such manufacture is generally effected by the technique of lapping or covering, which consists in winding at least one inextensible yarn or wrapping around an extensible yarn or core which is kept stretched. The wording extensible yarns includes any yarn which is naturally elastic, the other yarns being considered as inextensible. In particular the polyamide or polyester yarns, even if then are textured, are inextensible yarns. The wrapping has the function f limiting the extensibility of the composite yarn obtained and of delaying the ageing of the core When the latter consists of rubber or other material sensitive to the action of light, air and temperature during washing.

Success has recently lbeen achieved in producing synthetic fibres which have great extensibility and excellent resistance to ageing and are also remarkable for the persistence of their power to return, also called power of retention. Yarns formed of these libres, however, are costly and are at least as difficult to produce and to use for the manufacture of textile products (woven and knitted fabrics) as conventional yarns having a rubber base, in particular by reason of their great extensibility and the changes in the physical properties of these fibres 3,504,410 Patented Apr. 7, 1970 Summary of the invention It is an object of the present invention to produce composite covered yarns having an elastic core, which can be used directly for the manufacture of textile products, that is to say, which are mechanically stable on the loom and remain thermally stable in the course of possible subsequent treatment of the product (the size of which is practically speaking invariable for given tension conditions), and can be dyed if need be.

The invention also has as object thereof, the production of elastic twisted yarns in which the core comprises a percentage of elastomer distinctly less than that which is general at the present time for given elasticity characteristics, and it is therefore particularly advantageous in its applications to the case of relatively costly synthetic materials such as fibers having a polyurethane base.

The invention also has, as a further object, the provision of at least partially elastic textile products in which such yarns are incorporated and which exhibit properties which are a distinct advance in comparison with the products manufactured by the present techniques, from the point of View of both the manufacturer and the user, particularly as regards appearance, feel and power of return.

According to the invention an elastic core is given a twist before assembling it with at least one wrapping yam, which consists of any inextensi-ble material whatsoever, and effecting a thermal shrinking treatment in a non-oxidizing atmosphere, preferably by means of saturated steam. The shrunk yarn obtained in this way can still be dyed before knitting or weaving, its stability thus being remarkable and facilitating adjustment of the loom, -which is effected according to the product to be manufactured.

According to a particularly advantageous manner of carrying the invention into effect, the elastic core is first subjected to winding on a specially adapted machine, in the `course of which it is received on special spools, although it is possible to use standard spools. It then passes on to a twisting frame before being assembled in a single operation with at least one wrapping yarn consisting of inextensible material, without any restriction as to nature, or with two wrapping yarns, which wrapping yarns are wound around the core, preferably in opposite directions, the assembling machine being constituted by an improved throwing machine equipped with standard or improved hollow spindles. The shrinking of the yarn is effected on floats or discs and this has the unexpected result of considerably increasing the extensibility of the twisted yarn, while also improving its power of return.

Finally, the known property possessed by elastomeric yarns, of having their extensibility reduced by a thermal treatment effected in the stretched state on strong bobbins may also be applied, according to the invention, for bringing the extensibility of an elastic twisted yarn at least temporarily into a range suited to the manufacturer or user of textile products.

The invention also embraces textile products obtained by using such elastic yarns.

Brief description of the drawing FIGURE 1 is a diagrammatic diametral section of a spool used in the method of the invention, for winding the elastic core on a twisting frame;

FIGURE 2 is a diagram illustrating the details of the elastic yarn on this spool; t

FIGURE 3 is a diagrammatic elevational view of winding machine according to the invention;

FIGURE 4 shows in a similar manner, the special kinematic control system of the shaping apparatus which forms part of the machine shown in FIGURE 3;

FIGURE 5 is a diagram showing, in elevation, a throwing machine equipped with hollow spindles, which is adapted for assembling elastic twisted yarns with two wrapping yarns;

FIGURE 6 is a diagram showing the elongation of a twisted elastomeric yarn as a function of the tensile strength;

FIGURE 7 is a diagram showing the elongation of an untwisted elastomeric yarn as a function of the tensile strength;

FIGURES 8 to 10 represent on a considerably enlarged scale an elastic composite yarn according to the invention, in the free state, in a moderately stretched condition, and under its normal weaving or knitting tension, respectively;

FIGURES 11 and 12 show diagrammatically means for giving a practically constant tension to an elastomeric yarn.

Detailed description Referring to the drawings, the production of an elastic twisted yarn by the method of the invention, from starting materials coming from the spinning process, commences with winding the elastic yarn on spools or Ibobbins such as that shown in FIGURE 1. These spools are characteristed by the fact that the diameter of their cheeks or flanges 1a, 1b is scarcely larger than the diameter the ends 2e of the body (the difference being 40 mm. at the most and preferably only 2() mm.) and by the fact that the portions 2a, 2b of the body Iwhich are adjacent the ends form part of two conical surfaces which are opposed at their apices, the intermediate portions 2c being possibly cylindrical.

In carrying out the winding, considerable crossing is used, for example seven to twelve turns forward and back for a distance of 120 mm. between the cheeks, and a preferably slight tension is employed. The crossing results from the relative speeds at which the spools, on the one hand, and the yarn distributing apparatus, hereinafter called the shaping apparatus, on the other hand, are driven. Modern winding machines have separate motor and reduction gear sets for driving the spools and the shaping apparatus.

Such a machine is shown diagrammatically in FIG- URES 3 and 4, FIGURE 3 is an elevational view in which two bobbins or the like 10 filled with yarn from the spinning process are shown at the bottom, while at the top there are shown two spools or bobbins 11 with vertical axes, on to which the yarn passes as it is wound, and also a rocker 12 carrying guide eyes 13 for the yarns.

The use of an automatic tension regulator 25 enables a constant tension to be obtained.

At the output from this regulator there may be arranged a deeply grooved wheel 26 producing slight friction, which is preferably mounted on bearing balls and which has the effect of sparing the yarn by cutting off any friction force, and thereby of not modifying the tension at the output of the regulator and of bringing the final tension within the range sought, particularly in the case of an elastic yarn of high count.

FIGURE 4 illustrates an advantageous embodiment of the apparatus in which the rocker 12 is given a reciprocating movement suitable for distributing the yarn along the spools 11. The motor 14 operating the shaping apparatus drives, through the medium of a shaft 14a, a first shaft 15 on which a cam 16 is mounted by means of a key or splines, so as to be slidable on the shaft 15 while being driven in rotation by it, the said cam having at its periphery a continuous helical groove 16a. The distance a between the two points of the groove 16a which are furthest apart in the direction parallel to the shaft 15, determines the constant stroke a of the guide eye 13. A slide 17 carries a finger 17a engaging in the said groove and drives the depending arm of the rocker 12 in a manner which, for practical purposes, can be assumed to be a direct drive and which will be described in detail hereinafter.

As has been stated above, the helical cam 16 can slide on the shaft 15 which drives it in rotation. The cam carries a finger 16b engaging in a groove 18b in a part 18 mounted loosely on the shaft 15. The part 18 is driven by a second shaft 19, by means of a pinion 18o co-operating with a pinion 20 which has elongated generatrices and is fast with the shaft 19. The part 18 is provided at its periphery with a closed helical groove 18a in which a fixed linger 21 is inserted. The distance b between the two points of the groove 18a which are the furthest apart in the direction parallel to the shaft 15 determines the displacement b between the dead points of the yarn on a spool 11, this being called hereinafter, the cut-off of the shaping apparatus. The distance b' is at least equal to 1X5 of the stroke a. The ratio of the speeds of rotation of the helically grooved members 16 and 18 is advantageously 1/3, which is an exceptionally high value if it is compared with conventional values, which are of the order of 1/50.

If the periodic manner in which the yarn comes to the same distance from the cheeks of the bobbins were to assume too great a periodicity, this could cause irregularities of tension on the subsequent return of the yarn Wound on the spool; accordingly the winding machine also comprises an angle piece 22 which provides a connection between the slide 17 and the rocker 12, in parallel to that provided by the shafts 15 and 19. This angle piece is articulated at 22a to the slide 17 and it carries at 22b, a finger which co-operates with a slide on the depending .arm of the rocker. It also carries a third articulation point 22e which is advantageously adjustable in la direction perpendicular to the line 22a--22b. The articulation 22C connects the angle piece 22 to a ring 23 engaged on a third shaft 24. This shaft is eccentrically mounted, as shown in the drawing, and, moreover, it is driven in rotation from the shaft 15 by pinions which are designed in such manner that the speed ratio is very close to unity, with a difference of only a few percent. This difference is sufficient to produce -a slow displacement of the dead points of the yarn on the spool. Of course, the total stroke of the guide eye is adjusted in such manner that at the end of the winding operation the yarn 3 comes close to the cheeks 1a, 1b without touching them.

For low amounts of twist, the external diameter of the spool, when loaded with yarn, is of only relative importance but, if the yarn of the spool is to be twisted in a single operation to `a considerable value, which may reach 1,000 turns per metre, it is desirable that the external diameter of the spool, when loaded with yarn, should be at most equal to that of the cheeks. It is then sufficient to choose spools of rather large length or diameter, in order not to be hindered by these restrictions, it *being understood that a distance of mm. between the cheeks enables 300 grams of a conventional elastic yarn with a polyurethane base, of about 70 denier, to be wound under these conditions on a spool the body of which has a diameter of 50 mm. at the base 2e of the frustoconical parts 2a, 2b and 30 mm. at the top thereof.

The elastic yarn wound on the spool `and intended to form the core of the elastic twisted yarn is then twisted on a twisting frame. The spools described above make it possible to obtain a remarkably regular tension during this operation, even if the speed of rotation of the spindles reaches 10,000 r.p.m., and to adjust easily the twist of the core obtained in this way. The regularity of tension on the twisting frame is due mainly to the exceptionally large amount of the cross-over and to the value of the coeicient of friction of the elastic core against the upper cheek of the spool, which latter value is kept very low. The reception of this core is preferably effected on tubes, made of very strong material, for example metal with a setting of the pineapple type. These tubes have a minimum diameter of 50 mm. so as to avoid fatiguing the elastomer.

Twisting the elastic core has the effect of regularizing the mechanical characteristics to the elastomeric yarn. The count of elastomeric yarns, which are available on the market at the present time, is very irregular and varies Very much from one point to the other. The mechanical characteristics are shown on FIGURES 6 and 7 representing the elongation/tension curve of an elastomeric yarn, FIGURE 6 relating to a twisted yarn and FIGURE 7 to the same yarn maintained untwisted. Elongation is marked on the x-axis and tension on the y-axis.

The general shape of the two curves is the same. First the elongation increases with the tension which corresponds to the part AB of FIGURE 6 and A'B of FIGURE 7. Then the elongation decreases suddenly on account of the *breakage of the yarn; the abscissa of the point B or B is equal to the maximum elongation, the ordinate being the breaking tension.

The curves of FIGURES 6 and 7 have been obtained experimentally by testing one elastomeric yarn. The results of the tests are as follows:

grams. This result is not surprising for the twist produces an increase of the count of the yarn together with a decrease of the breaking elongation. Then the divergence between the maximum and the minimum -values of the elongation and the breaking tension'are reduced, which proves that twisting the elastic yarn regularizes the mechanical characteristics of said elastomeric yarn.

The assembly of the elastic core and the wrappings of inextensible material which are to form the elastic twisted yarn is effected on a special throwing machine equipped with hollow spindles which is illustrated in FIGURE 5.

This throwing machine comprises two stages in which the hollow spindles 4a and 4b, which are as nearly as possible vertical, are coaxial in pairs and are spaced from one another by a distance which is advantageously greater than 30 cm. Each stage is provided with a driving device 5a, 5b for the spindles, which devices are independent in speed and in direction of rotation.

The lower stage comprises an unwinding device 6 for the elastic core material 3, which is supplied wound on tubes and which passes through two spindles 31a, 31b in succession to receive its wrappings 32a, 32h, A constant unwinding tension can be obtained by means of an automatic tension regulator 7. A deeply grooved wheel set just before the rst hollow spindle can also 'be used. For the sake of simplicity, however, it is possible to use for all the spindles, counterweighttype braking or retarding means such as is usually employed in connection with unwinding apparatus, provided that the counterweights 8 which are employed all have accurate and identical calibrations. p

The unwinding tension is as close as possible to the breakage tension of the elastic core. It naturally varies as a function of the initial twist previously imparted to the core material and of the local characteristics of the fibres. A maximum working tension is generally adopted, such as will provide a margin suicient to prevent breakage due to local weaknesses in the core materials but which is ELASTOME RIC YARN 140 DENIE RS, TWISTzSOO TURNS PER METER [Twist measured on stretched yarn] Test number Arithmetical 1 2 3 4 5 6 7 mean Elongatiompercent 600 425 500 525 530 600 500 511 Breaking tension (grams) 150 145 130 135 142 145 145 142 ELASTOMERIG YARN 140 DENIERS UNTWISTED Test number Arithmetical 1 2 3 4 5 6 7 8 mean Elongation, percent 725 600 775 450 775 675 615 650 660 Breaking tension (grams) s. 130 150 135 120 150 125 115 135 132 The point B of FIGURE 6 corresponds to an elonnevertheless high enough to be economic, by reason of gation equal to 511%; the divergence `between the maxireduction in the percentage `by weight of elastic material mum value and the `minimum value is equal to 175%. The point B of FIGURE 7 corresponds to an average elongation equal to 660%; the divergence between the maximum value and the minimum value is equal to 325%.

The average breaking tension is equal to 142 grams for the twisted yarn (point B), the divergence between the maximum value `and the minimum value being equal to 2() grams. The average breaking tension is equal to 132 grams for the untwisted yarn (point B); the divergence between the maximum value and the minimum value being equal to 35 grams.

Twisting elastic core has then several effects. First the average elongation decreases from 660% to 511% and the average breaking tension increases from 132 grams to 142 in the twisted yarn. The latter is received on metal tubes carried by heavy spindles, so as to obtain a faultless drive.

As set forth previously, when assembling with the covering yarns, the elastic core is unwound with a tension which is practically constant and as close as possible to the breakage tension. FIGURES 11 and 12 show devices giving a practically constant tension to the elastic core,

According to FIGURE 1l, the spool, on which the elastic core is wound, is fitted on a shaft 27 which revolves in bearings 28. The yarn is drawn from this spool and is vbraked with counterweights 8 hung on wire loops 29 running over the shaft 27.

According to FIGURE 12, the core is elongated by means of a counterweight 8' hung on a pulley 30 around which the core runs after leaving the spool 3.

It will be observed that a gradual increase in the twist of the elastic core involves a corresponding gradual increase in its maximum working tension and in its power of return, at least up to a certain value of the twist which can be brought close to the saturating twist of conventional yarns. At the same time, the extensibility of the said elastic core is reduced by a substantially constant value with respect to the extensibility of the elastomer when free from twist. This value is about equal to 23% for the elastomeric yarn 140 deniers which has been tested.

The covering yarns may be any yarns.

Of course it is possible:

To wind one covering yarn around the elastic core, for example by using the device shown on FIGURE with one stage only;

To wind several parallel covering yarns around the elastic core for example `by using the device shown on FIGURE 5 with one stage only, the covering yarns being previously assembled on the same spool;

To wind one covering yarn on each stage around the elastic core, by using the two stages of the device of FIGURE 5;

To wind several covering yarns previously assembled on a spool on each stage of the device of FIGURE 5;

To wind one covering yarn on the first stage around the elastic core and to wind several covering yarns around the obtained composite yarn on the first stage, the covering yarns of the second stage being previously assembled on a same spool, or vice-versa to wind several covering yarns on the rst stage and one covering yarn on the second stage.

The composite yarns thus obtained have a characteristic appearance which depends on their tension as may be seen from FIGURE 8 to l0. In FIGURE 8 the yarn is in the relaxed condition and the covering yarns form a large number of loops. In FIGURE 9 the tension applied is moderate and the loops are still apparent. In FIGURE 10 the yarn is ready to be used on a loom, its tension is still higher and the loops are no more apparent.

For an extensibility of the composite covered yarn of at least 80%, the total count of the wrapping should not exceed six times the count of the core in the slack state. A count ratio of 2 appears to be the most advantageous.

The composite covered yarn can be subjected to a thermal shrinkage treatment. This treatment, which is also employed in the conventional technique, is effected using a twisted yarn previously placed on a iloat or on a bank, as it is done in the case of the usual yarns, and therefore in the slack state or on a deformable bobbin allowing shrinkage.

An autoclave is used from which the oxygen is carefully expelled by means of a vacuum pump with, if necessary, prior injections of steam. The treatment proper is carried out by means of steam, preferably saturated, which is injected in a quantity sufficient to obtain a rapid rise in temperature. The treatment lasts a few minutes, during which the temperature is maintained at a value about ten degrees at the most below the degradation temperature of the elastomeric synthetic fibres, which are generally the most fragile.

Cooling is carried out quickly, the composite yarn being removed from the autoclave at a low temperature, 50 C. for example.

According to a particularity of the invention, the composite covered yarns can be stabilized. For this purpose the covered yarns are maintained in a stretched state on rigid supports and they are submitted to a steam thermal treatment, preferably in an autoclave and in a non-oxidizing medium. This treatment is carried out slowly in the presence of saturated steam and under the following conditions:

Treatment temperatures comprised, for example, between 50 and 115 C.;

Treatment durations comprised, for example, between 5 and 120 minutes;

Cooling durations comprised, for example, between 20 and 60` minutes.

This treatment allows the elasticity of the composite yarn to be lowered, the yarn to be stabilized with suppression of the loops in the relaxed condition, and the wrapping yarns shrinkage ability to be limited 4when the wrapping yarns are made of a synthetic unshrunk material.

If such shrinking of the elastic twisted yarn in the stretched state, and a second shrinking without tension, are effected in succession, a final extensibility and a nal power of return are obtained which depend on the temperature of the treatment in the stretched state.

EXAMPLE I A composite covered yarn comprising a 70 denier elastomeric core and two covering yarns, each of them being an unshrunk 12 denier-4 filament polyamide 66 yarn, is made. The assembling of the core with the first covering yarn is made by winding said first covering yarn on the core in the S direction at a rate of 1200 turns/ meter, and by winding in the Z direction at a rate of 1200 turns/ meter for the second covering yarn. The composite covered yarn is treated to C. during 10 minutes and is completely stabilized. Its elastic power is substantially reduced to zero, its weaving or knitting much easier, the nal product recovering a certain elasticity ywhen dyed.

EXAMPLE II A composite covered yarn comprising a 70 denier elastomeric core and an unshrunk denier-46 ilament polyamide 66 covering yarn is made. The assembling of the core and the covering yarn is made by winding said covering yarn on the core in the S direction at a rate of 650 turns/meter. The composite covered yarn is subjected to a thermal treatment to 60 C. in a stretched state during 60 minutes, then slowly cooled during 60 minutes. A relatively inert yarn is obtained but the elasticity thereof in the fabric or knitwear is obsolutely not degraded; the shrinkage power of the covering yarn is still strongly high.

In the case where a naturally stable composite covered yarn is desired, the lapping winding presents a preferential value. When the single yarns constituting the composite covered yarn have an identical sense of twist and when the lapping winding is conventionally applied in the opposite sense, the preferential value is about 1700' turns per meter. When the single yarns have opposite sense of twist and -when the lapping winding is made in the opposite sense to that of the most heavily twisted single yarn by the hollow-spindle process, this preferential value is about 65 0 turns per meter.

Of course by using the two stages device of FIGURE 5, the mechanical stability of the composite covered yarn is easily obtained. Also it is obvious that the spindles can be rotated in same or opposite senses, to equal or different speeds, the twist of the core and of the first covering yarn b eing the same or opposite.

By modifying the twist of at least one of the single yarns constituting the composite covered yarn, the elastic characteristics of said twisted yarn can be controlled. For example augmenting the twist of the elastic yarn alone and reducing the twist of the assembled yarn, at least separately, reduces the stretch of the composite covered yarn and increases its retention strength for a given elongation. Conversely, reducing the twist in the elastic yarn alone and incerasing that of the composite yarn, at least separately, increases the stretch and reduces the retention force of said composite covered yarn for a given elongation.

Of course the carrying into practice of the yarns is made easier -when the workrooms are air-conditioned, due allowance to the fact that synthetic elastomeric yarns can 'be easily stretched on and above 25 C. The temperature of the workrooms is preferably equal to 25 C., and the hygrometrical ratio equal to 65%.

Weaving or knitting of such composite covered yarns is the easier as the yarns are stabilized with the hereinbefore conditions. Of course the fabric or knitting can then be subjected to a thermal treatment in a loose and unfolded condition, the temperature possibly reaching for a few tens of seconds the temperature producing the total shrinkage without damage to the less heat resistant textile liber. The heating and the cooling are as quick as possible.

For manufacturing a textile product, by weaving or knitting, it is fo course possible to use composite covered yarns which are S- or Z-covered, or to use S- and Z-twisted composite yarns preferably perfectly symmetrical and produced under conditions identical from every standpoint (spindle rotation speeds, tension, adjustment of the overlap controlling devices, spool hardness). Using symmetrical S and Z twisted composite yarns enables the obtainment of uniform woven and knitted fabrics.

A thermal stabilization treatment of the composite covered yarns may be performed, preferably at a measured temperature in degrees centigrade on the Celsius scale that is less than 40% of the temperature producing total shrinkage without damage to the most fragile synthetic fiber. constituting the yar-n and the thermal treatment of the woven or knitted fabric is performed in an autoclave.

Weaving or knitting can be performed in such a way that the tension force is equally distributed between the single yarns which form the composite covered yarn. It will be noted that the braking elongation is practically the same for the elastic core and the covering yarn.

EXAMPLE III Composite Single yarns yarns Lycra core (70 deniers 2,200 t./m. S) Nylon wrapping (7o deniers 65o wm. Z) 650 t-/m- Z- Lycra core (70 deniers 2,200 t./rn. Z) 650 t /m S Nylon wrapping (70 deniers 650 t./m. S)

`It will be noted that both the elastic core and the inextensible wrapping are twisted before assembling and that the elastic core is more twisted than the covering yarn.

It will be also noted that the assembling twist of said core and said wrapping is of opposite sense to that of said elastic core whereby to form a mechanically stable composite yarn.

With these composite yarns a fabric is obtained, the warp comprising alternately a S-twisted yarn and Z- twisted yarn, the weft being made with wool yarns.

The fabric is heat treated to 118 C. for one minute, such temperature being obtained in 30 seconds.

EXAMPLE IV A composite covered yarn is made according to the following table.

EXAMPLE V A composite covered yarn is made according to the following table Composite Single yarns yarns Lycra core (70 deniers 650 t./m. Z)

Nylon wrapping 150 deniers spinning twist 650 wm' S' The composite yarn is subjected to a thermal treatment to 60 C. during 60 minutes in a stretched state.

EXAMPLE VI A composite covered yarn is made according to the following table l Composite Slngle yarns yarns Lycra core (650 t./m. Z, 70 deniers) 1,200 t./m. S. First wrapping: Nylon 12 deniers spinning twist Second wrapping: Nylon 12 deniers spinning twist 1,200 t./m. Z.

The composite covered yarn is heat shrunk in a free state to 115 C. during 2 minutes.

EXAMPLE VII A composite covered yarn is made according to the following table Composite Single yarns yarns Lycra core ('.70 deniers 650 t./m. Z) 1,200 t./m. Z. First wrapping: Nylon 12 deniers spinning twist" Second wrapplng: Nylon 12 deniers spinning twist 1,200 t./m. S.

The composite yarn is subjected to a thermal treatment up to C. during 10 minutes in a stretched state. It is then subjected to another thermal treatment up to C. during 2 minutes, in a free state.

Yarns which are not particularly elastic may be incorporated into the woven or knitted fabric.

The composite covered yarns according to the present invention may be utilized for knitting or weaving indifferently symmetrically, or not, and provide a wide variety of weave patterns. They may be alternated mutually or with conventional yarns.

In addition to the appearance peculiar to them, referred to precedingly, the woven or knitted fabrics obtained thus have adjustable degrees of elasticity. Obviously, if elasticity alone is sought without a` crepe effect, the composite yarns specified in Example V will be most suitable. Such elasticity may correspond with a more or less large percentage of elasticity yarns used only in the weft or the warp of the textile product, possibly in alternation with different yarns. It could also correspond with more or less large percentages of elastic yarns utilized in both the weft and the warp of the textile, the percentages possibly differing in weft and warp.

The examples given in the following table have been chosen to illustrate the results which are obtained by using two covering yarns.

The primary twist is the initial twist of the Wrapping yarn, and the spinning twist is the twist of the yarn obtained on a spinning frame at the output of a spinneret. This twist is very low (less than 20 turns/meter).

TABLE Elastomer Wrapping Extensibility Tests After Aiter n 10 mins. 10 mins. leaving at at Count in Lapping frame, 85 C., 110 C Example denier Twist Nature and count in denier winding Primary twist percent percent percent a 70 @50S {lmdei? 1.5' 21111111121 ".2:

Polyamide, 2 x 150 980 Z b 70 650 S -.-.o 980 S Polyamide, 2 x 20 980 Z c 70 6508 ...-l 980S d d manpflrefeftff--- e 70 650 S So-called false twist textured polyhexamethylene 650 Z Spinning twist 240 260 f 140 500 S adpamide, 2 x 30. 65 s d Conventional textured 11-aminoundecanoic acid di- 650 Z Spinning twist 240 300 g 140 500 S arine, 2 x 63. S d

Conventional textured l polyhexamethylene adipaznide, 650 Z do 240 290 h 140 500 S l x 63.

Crnv tional textured 1 polyhexamethylene adipamide, 650 S do i 70 650 s Raw polyhexamethylene adipamide, 1 x 20, 7laments. 650 Z .do 160 240 Rawpolyhexamethyleneadipamide, 1x40,13filaments 650s d0 j 70 {650 S Polyamide, 1 x 150 650 Z -do (650 Z) do (650 S) do 60 160 Cotton, 2 x Nm 60 580 Z k 70 650 S go 580 S 1 70 650 S {trlc' 2 x Nm 6"""::::""':':':::"'m'i' 533 m 14 200 S {Y' Nm 5'''131:'1'1331123132222:'13:23:11 S

n 140 500 s Raw polyhexamethylene adipamide, 1 x 70, 34 filaments. 650 Z Raw polyhexarnethylene adipamide, 1 x Nm, 50 wool.. 650 S lMultitilament, twisted, xed by heat and untwisted ln succession.

The table calls for the following further remarks and permits the following facts to be established:

In all the examples, the elastic core is a continuous multi-filament yarn of polyurethane base and having an Stwist, it being understood that the core can also be Z-twisted.

In Example a, the tension of the core during assembly is grams, the lower spindle rotating at 7900 r.p.m. in the opposite direction to the core and the upper spindle rotating at 6500 r.p.m. in the same direction as the core. The shrinking treatment is effected on floats 1.40 metres in circumference by means of saturated steam.

The elasticity obtained after shrinking of the constituents of the elastic twisted yarn is quite remarkable, the weight of the elastic core amounting to only 4.5% of the total weight of the twisted yarn, which may be compared from the point of view of elasticity to a conventional textured 2/ 63 mousse synthetic polyamide yarn (the elasticity of which yarn arises from the fact that the multiple bres from which it is formed, which may be regarded, for practical purposes, as inextensible, are twisted, xed by heat and then untwisted in succession). The elastic yarn of the invention has a cost lower than that of the textured yarn, in spite of the twisting of the core prior to assembly.

A comparison of Examples a and b or d and e shows the influence of the lapping winding on the extensibility of the twisted yarn.

A comparison of Examples b and c shows the effect on the extensibility of the twisted yarn, of the count of the wrapping (which is advantageously limited, as has been stated above).

Examples d to l1 relate to yarns having wrappings which have been subjected to a texturing treatment, giving them artificially a limited extensibility. This treatment can be carried out in a plurality of operations, or on an improved machine, in which case one speaks olf false twist. The high value of the extensibility nally obtained will be observed from the table.

Two wrappings used together may have different counts, as illustrated by Examples h and i.

Example j relates to a yarn having one covering yarn, to which the shrinking treatment of the elastomeric yarn, which forms an important stage in the method of the invention, may also be applied.

Examples k to n relate to various natural and synthetic discontinuous wrappings. The yarn of Example n is shrunk under tension, which gives it a close appearance.

It will be understood that the invention is not limited to the embodiments which have been particularly described, but that it covers also modications thereof which can be obtained, by the use of equivalent technical means.

What is claimed is:

1. A method of manufacturing elastic textile fabrics, comprising the successive steps of twisting a yarn made orf a synthetic shrinkable elastic material, twisting a yarn of inextensible material a lesser degree than that of said elastic yarn, covering said elastic yarn while stretching it close to breakage with said inextensible yarn, said inextensible yarn being lapped around said elastic yarn in a direction opposite to the direction in which said elastic yarn is twisted to form a rst composite covered yarn, preparing a second composite covered yarn in a similar way from a yarn made of a synthetic shrinkable elastic material and a yarn of inextensible material, said yarn of elastic material of said second composite covered yarn being twisted in a direction opposite to the direction in which the elastic yarn in said first composite covered yarn is twisted, manufacturing textile fabrics comprising said first and second composite covered yarns in an alternate manner, heating said textile fabrics in an unstretched state with steam to the temperature of total shrinkage of the synthetic shrinkable elastic materials for a period of at most a few minutes and in a nonoxidizing atmosphere, and rapidly cooling said textile fabrics.

2. The method as claimed in claim 1, wherein said elastic and said inextensible yarns jointly constituting a composite covered yarn are twisted in the same direction, and wherein the lapping winding is about 1700 turns/ meter.

3. The method as claimed in claim 1, wherein said elastic and said inextensible yarns jointly constituting a composite covered yarn are twisted in opposite directions, and wherein the lapping winding is about 650 turns/ meter.

4. The method as claimed in claim 1, wherein said textile fabrics are manufactured on a loom while imparting to each composite covered yarn a tension which is equally distributed between its respectively elastic and inextensible constituent yarns.

5. The method as claimed in claim 1, wherein said synthetic elastic yarn is free from any shrinkage prior to the beginning of the present method.

6. The method as claimed in claim 1, further comprising the step of thermally treating said composite covered yarns in a stretched state with steam at a ternperature less than 40% of the temperature which is applied during the subsequent step of heating said textile fabrics, as measured in degrees Centigrade on the celsius scale.

7. A method of manufacturing elastic textile fabrics, comprising the successive steps of twisting a yarn made of a synthetic shrinkable elastic material, twisting a yarn of inextensible material a lesser degree than that of said elastic yarn, covering said elastic yarn while stretching it close to breakage with said inextensible yarn, said inextensible yarn being lapped around said elastic yarn in a direction opposite to the direction in which said elastic yarn is twisted to form a composite covered yarn, manufacturing textile fabrics comprising said composite covered yarn, rapidly heating said textile fabrics in an unstretched condition with steam to the temperature of total shrinkage of the synthetic shrinkable elastic material for at most a few minutes and in a non-oxidizing atmosphere, and rapidly cooling said textile fabrics.

8. The method as claimed in claim 7, wherein said elastic and said inextensible yarns jointly constituting the composite covered yarn are twisted in the same direction.

9. The method as claimed in claim 7, wherein said synthetic elastic yarn is free from any shrinkage prior to the beginning of the present method.

10. The method of manufacturing an elastic composite yarn comprising the successive steps of twisting a yarn made of a synthetic shrinkable elastic material, covering said elastic yarn while stretching it close to breakage, with at least one covering yarn of an inextensible material to form a composite covered yarn, rapidly heating said cornposite covered yarn, in an unstretched condition with steam to the temperature of .total shrinkage ofthe synthetic shrinkable elastic material for at most a few minutes and in a non-oxidizing atmosphere, and rapidly cooling said composite covered yarn.

11. The method as claimed in claim 10, which further comprises, before the above-mentioned heating strep, the

step of thermally treating the composite covered yarn in a stretched state with steam at a temperature less than 40% of the temperature which is applied during the subsequent heating step, as measured in degrees Centigrade on the celsius scale.

References Cited UNITED STATES PATENTS MERVIN STEIN, Primary Examiner USS. Cl. X.R. 57-152, 163 

